Lithium secondary batteries use materials capable of reversibly intercalating or deintercalating lithium ions in cathode and anode, and include an organic electrolyte solution or a polymer electrolyte for transfer of lithium ions between the cathode and anode. Lithium secondary batteries generate electrical energy by an oxidation/reduction reaction during the intercalation/deintercalation of lithium ions at the cathode and anode.
For a cathode active material of a lithium secondary battery, metal chalcogenide compounds being capable of intercalating and deintercalating lithium ions are generally used. Examples of the compounds include commercialized composite metal oxides including a cobalt-based compound such as LiCoO2, and the like, a manganese-based compound such as LiMn2O4, LiMnO2, and the like, and a nickel-based compound such as LiNiO2, LiNi1-xCOxO2 (0<x<1), and the like.
Generally, the cathode active material is prepared according to a solid-phase synthesis method or a wet synthesis method. When it is prepared according to the solid-phase synthesis method, a starting material for synthesizing the cathode active material and secondary phases produced at a low temperature may be maintained at a high temperature, so that it is difficult to control the uniformity of particle size and dispersion when the starting material has a large particle size. In order to solve the problems and to provide a cathode active material such as a single phase LiMn2O4 powder, it may be prepared according to the low temperature synthesis method.
The method of synthesizing a cathode active material at a low temperature generally uses a wet method. The wet method may include a sol-gel method, precipitation, a Pechini process, a hydrothermal process, an emulsion-drying method, a melt-impregnation method, a combustion method, a citric acid method, and the like. The wet method may synthesize a cathode active material such as a single phase LiMn2O4 powder having excellent crystallinity, homogeneity, and uniform shape distribution of a micron or less, but the methods have many problems of cost, time, and a complicated process.